1. Field of Invetion
The invention relates to an apparatus for the elimination of substances from liquids, in particular from blood.
2. Description of the Prior Art
Blood treatment devices are already known in which blood is first guided into a primary extracorporeal circuit through a hemodialyzer or a hemofilter. The second chamber of the filter is part of a secondary circuit in which only specific components of the blood are circulated. The actual blood treatment elements such as adsorber elements are provided in this secondary circuit. The split into two circuits can be necessary if the adsorber elements should not come into contact with the full blood, but with the blood plasma.
Such an apparatus is, for example, already known from EP 0 776 223 B1. Here, a primary circuit for the liquid to be treated is present with a filter integrated therein. A secondary circuit in which at least one adsorber is arranged is connected to the secondary side of the filter.
A corresponding apparatus as described in FIG. 1 is known. A primary circuit 12 is shown there in which the liquid of the primary circuit, for example blood, is circulated by the pump 16. A filter 10 is integrated in the primary circuit. A secondary circuit 14 in which the liquid of the secondary circuit is circulated at a constant volume via a roller pump 18 adjoins the secondary side of the filter 10. Two adsorber elements 38 and 40 for the purification of the liquid of the secondary circuit 14 are integrated in the circuit. With this arrangement, a specific pressure gradient is adopted in the hemofilter, with an infusion of secondary liquid into the blood circuit taking place in the upper part of the filter (inlet of the secondary liquid) and a removal of liquid from the blood circuit taking place at the lower end (outlet of the secondary liquid). The replaced volumes balance precisely due to the constant volume. It is, however, a disadvantage that the absolutely replaced liquid volume, and thus the purified liquid volume, is not precisely defined.
Whereas the detoxification of blood is possible with serious liver failure using the filter 10, a hemodialyzer 42 can additionally be arranged in the primary circuit, as shown in FIG. 1 in accordance with the prior art, by means of which hemodialyzer water soluble toxins can be removed from the blood with the help of a dialysis machine via the extracorporeal blood circuit.